- class Commitment p where
- class (Functor p, Monad p, Applicative p, Alternative p, Commitment p) => PolyParse p
- apply :: PolyParse p => p (a -> b) -> p a -> p b
- discard :: PolyParse p => p a -> p b -> p a
- failBad :: PolyParse p => String -> p a
- adjustErrBad :: PolyParse p => p a -> (String -> String) -> p a
- indent :: Int -> String -> String
- oneOf :: PolyParse p => [p a] -> p a
- exactly :: PolyParse p => Int -> p a -> p [a]
- upto :: PolyParse p => Int -> p a -> p [a]
- many1 :: PolyParse p => p a -> p [a]
- sepBy :: PolyParse p => p a -> p sep -> p [a]
- sepBy1 :: PolyParse p => p a -> p sep -> p [a]
- bracketSep :: PolyParse p => p bra -> p sep -> p ket -> p a -> p [a]
- bracket :: PolyParse p => p bra -> p ket -> p a -> p a
- manyFinally :: PolyParse p => p a -> p z -> p [a]
- manyFinally' :: PolyParse p => p a -> p z -> p [a]
The PolyParse classes
Commitment class is an abstraction over all the current
concrete representations of monadic/applicative parser combinators in this
package. The common feature is two-level error-handling.
Some primitives must be implemented specific to each parser type
(e.g. depending on whether the parser has a running state, or
whether it is lazy). But given those primitives, large numbers of
combinators do not depend any further on the internal structure of
the particular parser.
Commit is a way of raising the severity of any errors found within its argument. Used in the middle of a parser definition, it means that any operations prior to commitment fail softly, but after commitment, they fail hard.
p applies the transformation
f to any error message
p, having no effect if
Parse the first alternative that succeeds, but if none succeed, report only the severe errors, and if none of those, then report all the soft errors.
PolyParse class is an abstraction gathering all of the common
features that a two-level error-handling parser requires:
the applicative parsing interface, the monadic interface, and commitment.
There are two additional basic combinators that we expect to be implemented
afresh for every concrete type, but which (for technical reasons)
cannot be class methods. They are
Combinators general to all parser types.
Apply a parsed function to a parsed value. Rather like ordinary function application lifted into parsers.
x parses both x and y, but discards the result of y.
const lifted into parsers.
When a simple fail is not strong enough, use failBad for emphasis. An emphasised (severe) error cannot be overridden by choice operators.
adjustErrBad is just like
adjustErr except it also raises the
severity of the error.
Helper for formatting error messages: indents all lines by a fixed amount.
'exactly n p' parses precisely n items, using the parser p, in sequence.
'upto n p' parses n or fewer items, using the parser p, in sequence.
Parse a list of items separated by discarded junk.
Parse a non-empty list of items separated by discarded junk.
Parse a list of items, discarding the start, end, and separator items.
Parse a bracketed item, discarding the brackets.
If everything matches except the closing bracket, the whole
parse fails soft, which can give less-than-satisfying error messages.
If you want better error messages, try calling with e.g.
bracket open (commit close) item
manyFinally e t parses a possibly-empty sequence of
terminated by a
t. The final
t is discarded. Any parse failures
could be due either to a badly-formed terminator or a badly-formed
element, so it raises both possible errors.
manyFinally' is like
manyFinally, except when the terminator
parser overlaps with the element parser. In
manyFinally e t,
t is tried only when parser
e fails, whereas in
manyFinally' e t, the parser
t is always tried first, then
e only if the terminator is not found. For instance,
manyFinally (accept 01) (accept 0) on input
manyFinally' with the same arguments
and input returns